At 16, my innocence was shattered when two gunmen murdered 13 people at my school and wounded countless others.

Columbine High School promised to be a safe and secure place of learning. And that promise was broken on April 20, 1999.

On that morning, I headed to school worried about my 10th grade math test and my upcoming track meet. Useless worries: The test was never given and we never held the meet.

Scars remain from that day that no one can see. Scars that made my worries about math tests or track performance pale in comparison to whether my science partner would live or whether my classmate's speech would be impaired by the shrapnel lodged in his skull. Today, those mental scars throb in large crowds and force me to scan the room for exits. They make my heart beat faster when I hear the blades of a helicopter overhead.

Katie Lyles

Now, as a teacher in my eighth year in the classroom, I consider every day that I go to work a privilege. I cherish my students' joy and enthusiasm, and most importantly, their innocence.

I believe that it is our job, as a society, to protect these virtues in our young people. I want them to be worried about math tests and track meets and about science fairs and student council elections -- the kind of normal school stuff that builds character. But our epidemic of gun violence is creating a culture of fear in our schools, where students are anxious about safety and intruders. These are worries no student should have.

This becomes even more apparent when we conduct our monthly emergency drill at our school. It's a way to be prepared for the worst, so we practice lockdowns, fire drills and evacuations.

The other day, I was explaining to my third graders that we were going to practice a lockdown just in case a bear happened to be on the playground -- a real scenario for our Colorado school. I have used this example my entire teaching career because it's an easy and nonthreatening reason to practice a lockdown.

One girl raised her hand and asked: "Is this what we would do if a bad guy came with a gun to hurt us?" I felt kicked in the stomach when I heard this question. A bear is no longer the worst thing for students to anticipate: They fear what is happening across our nation.

It is a shame that my students must learn these drills at such a young age -- a shame they must learn them at all. I thought to myself, "This is a result of the Columbine shootings, along with so many other acts of violence. This is my reality, and now it is theirs too."

It is a sad reality, but we are not helpless. I teach at a wonderful school, which has done everything within its resources to keep our students safe. But it is not enough. If there were a simple solution, then this epidemic of violence would have ended. The solution is complex, multifaceted -- and achievable. I believe a comprehensive approach can help ensure a safe learning environment.

•Our children deserve more mental health resources to identify, treat and follow up with people who need help.

•Our children deserve enhanced school security: This includes identifying who is in the school and sensible steps to keep the building secure -- without bringing guns into the place of learning or turning it into a fortress.

•Our children deserve common sense gun legislation: I believe this should include a ban on high-capacity magazine clips. And at the very least, it should include comprehensive and enforceable background checks to help keep guns out of the hands of dangerous people. Unfortunately, our Congress refused to take this common sense step and turned this legislation down.

The shooters at my school obtained their guns illegally, through private sales and straw purchases. Today they could easily go online and buy those same weapons without a background check. What is to stop the next person who chooses from doing just that?

We can do better.

I think I can speak for all of us that the murders at Columbine High School, the Aurora movie theater, Sandy Hook Elementary, and so many others shocked us to our core and created lasting feelings of sadness. But we can't let these events create feelings of vulnerability. We have the power to work together to create a safer world for our students.

Learn from my experience -- do not wait until you experience violence first hand to realize that we need to take action. We need to take action now.